But big donations are, indeed, pouring in. Campaign finance statements recently filed by United for Missouri's Priorities, the campaign opposing Sinquefield's efforts, show major donations in recent weeks -- bringing the group's total revenue to a number just shy of $1 million to date.

The pro-earnings tax campaign got its biggest donation from the United Education Association in Washington, D.C., which chipped in $200,000.

Its next biggest contribution came from AFSCME,
the division of the AFL-CIO representing state, county and municipal
employees. AFSCME's put in $115,000 to date, campaign finance reports
show. The Greater Kansas City chapter of the AFL-CIO added another $25,000.

Other big donors? The branch of the International Association of Fire Fighters based in Kansas CIty has kicked in $70,000, with donations from both its political wing and the union itself. The Missouri Council of State Firefighters chipped in another $20,000.

Missouri Federation of Teachers has given $55,000; the Missouri National Education Association donated $50,000.

Among employers, BJC Healthcare -- which owns Barnes-Jewish Hospital -- and Washington University donated $25,000 and $5,000 respectively. The Civic Council of Greater Kansas City donated $40,000.

Mark Jones, campaign manager for the pro-earnings tax/anti-Sinquefield group, says he expects to see even more donations from business groups. "We really have been proud of the coalition we've brought together," he says. "The business community has realized the danger of Proposition A, and they've organized to fight against it."

If approved by state voters in November, Prop A would force Kansas City and St. Louis to bring their earnings taxes -- which tax city residents at an additional one percent of their income each year -- to a citywide vote every five years. It would also bar other municipalities in Missouri from enacting such taxes in the future, Jones says.

"I think what [these donations] are a reflection of is how overly invasive Prop A is," Jones says. "You've got one person who has an economic theory, and he wants to use Missouri as a laboratory. But he's insulated from the consequences of this theory when it goes horribly awry."

The earnings tax currently provides about 30 percent of the general revenue in both Kansas City and St. Louis, Jones says.

The latest campaign finance report for Sinquefield's "Let Voters Decide" group was filed Friday. It shows the group still has $4.4 million on hand, despite spending about $106,000 on Chesterfield public relations firm Common Ground, $175,000 on Blitz, Bardgett and Deutsch for legal services and $4.4 million on campaign consultants Winner & Mandabach.

That company, based in Santa Monica, California, claims on its website to boast a 90 percent winning percentage. Which, coupled with Sinquefield's apparently endless donations, means that the opposition campaign is going to need every last cent it gets.